title: Hydroperoxide-dependent epoxidation of unsaturated fatty acids in the broad bean (Vicia faba L.).
abstract: Incubation of linoleic acid with the 105,000g particle fraction of the homogenate of the broad bean (Vicia faba L.) led to the formation of the following products: 13(S)-hydroxy-9(Z),11(E)-octadecadienoic acid, 9,10-epoxy-12(Z)-octadecenoic acid (9(R),10(S)/9(S)/10(R), 80/20), 12,13-epoxy-9(Z)-octadecenoic acid (12(S),13(R)/12(R)/13(S), 64/36), and 9,10-epoxy-13(S)-hydroxy-11(E)-octadecenoic acid (9(S),10(R)/9(R),10(S), 91/9). Oleic acid incubated with the enzyme preparation in the presence of 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid or cumene hydroperoxide was converted into 9,10-epoxyoctadecanoic acid (9(R),10(S)/9(S),10(R), 79/21). Two enzyme activities were involved in the formation of the products, an omega 6-lipoxygenase and a hydroperoxide-dependent epoxygenase. The lipoxygenase, but not the epoxygenase, was inhibited by low concentrations of 5,8,11,14-eicosatetraynoic acid and nordihydroguaiaretic acid. In contrast, the epoxygenase, but not the lipoxygenase, was readily inactivated in the presence of 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid. Studies with 18O2-labeled 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid showed that the epoxide oxygens of 9,10-epoxyoctadecanoic acid and of 9,10-epoxy-13(S)-hydroxy-11(E)-octadecenoic acid were derived from hydroperoxide and not from molecular oxygen.
authors.affiliation: Department of Physiological Chemistry, Karolinska Institutet, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Hamberg
authors.forename: G
authors.initials: G
authors.lastname: Hamberg
mesh_terms: D015117:5,8,11,14-Eicosatetraynoic Acid / Q000494:pharmacology; D002855:Chromatography, Thin Layer; D003600:Cytosol / Q000378:metabolism; D004852:Epoxy Compounds / Q000302:isolation & purification / Q000378:metabolism*; D007887:Fabaceae / Q000378:metabolism*; D006880:Hydroxy Acids / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism*; D009637:Masoprocol / Q000494:pharmacology; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism*; D010946:Plants, Medicinal
chemical_list: D004852:Epoxy Compounds; D006880:Hydroxy Acids; D008041:Linoleic Acids; D009829:Oleic Acids; D015117:5,8,11,14-Eicosatetraynoic Acid; D019301:Oleic Acid; D009637:Masoprocol; D019787:Linoleic Acid